A wide variety of cardiac pacemakers are known and commercially available. Pacemakers are generally characterized by which chambers of the heart they are capable of sensing, the chambers to which they deliver pacing stimuli, and their responses, if any, to sense intrinsic electrical cardiac activity. Some pacemakers deliver pacing stimuli at fixed, regular intervals without regard to naturally occurring cardiac activity. More commonly, however, pacemakers sense electrical cardiac activity in one or both of the chambers of the heart, and inhibit or trigger delivery of pacing stimuli to the heart based on the occurrence and recognition of sensed intrinsic electrical events. A so called "VVI" pacemaker, for example, senses electrical cardiac activity in the ventricle of the patient's heart, and delivers pacing stimuli to the ventricle only in the absence of electrical signals indicative of natural ventricular contractions. A "DDD" pacemaker, on the other hand, senses electrical signals in both the atrium and ventricles of the patient's heart, and delivers atrial pacing stimuli in the absence of signals indicative of natural atrial contractions, and ventricular pacing stimuli in the absence of signals indicative of natural ventricular contractions. The delivery of each pacing stimulus by a DDD pacemaker is synchronized with prior sensed or paced events.
Pacemakers are also known which respond to other types of physiological based signals, such as signals from sensors for measuring the pressure inside the patient's ventricle or measuring the level of patient's physical activity. These labelled "VVIR" for a single chamber version or "DDDR" for a dual chamber version.
The complexity of modern pacemakers, the need to diagnose, optimize and adjust various parameters during the implant procedure, the occurrence of rare device failures, or more commonly, physiologic changes, and device variables or drift, dictate the need for numerous programmable parameters accessible non-invasively via an externally operated programmer. The need to assess system performance or troubleshoot the patient, device and/or lead system in an acute, clinical setting requires extensive telemetry capability in the implanted device and external programmer.
Modern programmers used to adjust the parameters of multi-function implantable medical devices, typically have graphic displays, keyboards or light pens for data entry and device control by operator manipulation, and printers or plotters to allow the user to easily control, evaluate and document the extensive capabilities of modern medical devices. An example of one such device is the Medtronic Model 9760 programmer. Typically, in use during an implant procedure in the surgical suite, the programmer is positioned outside the sterile field remote from the patient. A programming head, or wand containing transmitter and receiver circuitry, is connected to the programmer via a stretchable coiled cable, and positioned over the patient's pacemaker implant site for programing or telemetry interrogation of the implanted device. The programmer typically consists of 1 or more microprocessors and contains programmable memory capable of storing executable programs under the control of the operator via keyboard or light per entry. The physician in the sterile field verbally communicates programming directions to a nurse or associate at the control of programmer outside of the sterile field. The implanting physician often cannot see the screen or display on the programmer because of the distance involved, small size of the screen, or display screen contrast limitations. This requires the program operator to verbally communicate patient status, device function and status, and success or failure of requested program operations to the physician.
Similarly, during an implant, a Pacing Systems Analyzer (PSA) is typically used to verify cardiac pulse generator function and evaluate lead pacing threshold and intrinsic signal amplitude values. These values are utilized to set the programmable parameters of the implantable pulse generator to ensure an adequate safety margin for pacing and sensing, respectively. In use, the PSA is connected by test cables to the externalized proximal end of the lead system implanted in the patient. The PSA is held and controlled by an assistant who reports stimulation thresholds and R-wave/P-wave amplitudes on a beat-by-beat basis. The PSA typically contains pacing and sensing circuitry, under control of one or more microprocessors, and programmable memory capable of storing executable programs under the control of the operator via keyboard entry. This process is error prone due to the potential errors in the viewing of values on a small liquid crystal display (LCD) on a typical PSA and the verbal communication required to report to the attending physician.
In prior art, as the programmer operator enters strings of keystrokes to control the operation of the programmer, to set up programmable parameter values for the implanted device or to program or interrogate the implanted device, programmers have used an audio tone or "beep," either intermittently or steady, to confirm programmer and/or implanted device function and status. Examples of prior art audio feedback include U.S. Pat. No. 4,236,524 to R. Powell, et al., "Program Testing Apparatus"; U.S. Pat. No. 4,250,884 to J. Hartlaub, et al., "Apparatus For and Method of Programming the Minimum Energy Threshold For Pacing Pulses to be Applied to a Patient's Heart"; U.S. Pat. No. 4,305,397 to S. Weisbrod, et al., "Pacing Generator Programmer With Transmission Checking Circuit"; and U.S. Pat. No. 4,323,074 to G. Nelms "Pacemaker Programming Apparatus Utilizing a Computer System with Simplified Data Input"; all assigned to the assignee of the present invention and incorporated herein in their entirety by reference. All operate, or sound, a beeper for valid keystroke entries. The '884 and '397 patents also describe sounding a beeper to indicate programmer status such as a valid downlink programming or the completion of a timeout function. The '074 patent also describes sounding a beeper to indicate a successful battery check operation upon device turn-on. Additionally, U.S. Pat. No. 4,432,360 to U. Mumford, et al., "Interactive Programmer for Biomedical Implantable Devices" describes intermittently sounding a beeper upon power-up/self-test and at specific device function/status such as programming "STAT SET" or standard values. Additionally, a steady tone is sounded at the transmission of programming pulses and a pulsating tone at the end of transmission or during self-test failure. With the previously listed needs and shortcomings of prior art programmers and analyzers, the use of intermittent or steady tones is inadequate to meet complex present day requirements for patient safety and communication.
These and other problems are solved by the apparatus of this invention.